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DEVELOPMENT AND COMPETITION IN RICE WEEVIL, Sitophilus oryzae (L.) AND RED FLOUR BEETLE, Tribolium castaneum (Herbst), AND THEIR RESPONSES TO ACTIVE
COMPOUNDS IN SELECTED SPICES.
NELLIE WONG SU CHEE
UNIVERSITI SAINS MALAYSIA
2016
DEVELOPMENT AND COMPETITION IN RICE WEEVIL, Sitophilus oryzae (L.) AND RED FLOUR BEETLE, Tribolium castaneum (Herbst), AND THEIR RESPONSES TO ACTIVE
COMPOUNDS IN SELECTED SPICES.
by
NELLIE WONG SU CHEE
Thesis submitted in fulfilment of the
requirements for the degree
of Doctor of Philosophy
2016
ii
ACKNOWLEDGEMENTS
I would like to express my gratitude to my main supervisor, Professor Lee
Chow Yang for his supervision, advices and guidance throughout the course of my
studies. Thank you for the many suggestions and the opportunity to carry out my
PhD. studies under your assistance.
I would also like to thank my co-supervisor, Dr. Lim Gin Keat for his help
and advices, especially regarding the chemical aspects of my study. A big thank you
too to the staff of School of Biological Sciences, especially Ms. Anna (Biochemical
Laboratory), En. Nazeef (MUPA laboratory, School of Chemical Sciences) and En.
Fisal (School of Pharmaceutical Sciences, Chemistry) for their technical assistance
and equipment support. I would like also like to thank USM and ACT (Agricultural
Crop Trust) for providing me with financial assistance during my study period.
My thanks to my friends from the Urban Entomology Laboratory, Hui Siang,
Jia Wei, Xin Yu, Ching Chen, Veera, Nadiah and Foong Kuan, for your
companionship and sharing the laboratory life with me. Special thanks to my friends,
Ru Yuan and Boon Hoi for online chats with me that made life so much interesting.
I am also very grateful to my mum and dad for helping out, especially with
the caring of Nicole while I studied. Thank you to Chris for accompanying and
cheering me all the way. I would like to thank my brother, Alan for giving me words
of wisdom and who always makes sure I am thinking carefully, rationally and
calmly. To my Nicole, mama loves you lots and lots!
I give thanks and praise to the Lord for always being there for me at all times.
May You continue to guide me throughout my life. Amen.
iii
TABLE OF CONTENTS
Page ACKNOWLEDGEMENTS
ii
TABLE OF CONTENTS
iii
LIST OF TABLES
vii
LIST OF FIGURES
ix
LIST OF PLATES
xii
LIST OF ABBREVIATIONS
xi
ABSTRAK
xv
ABSTRACT
xvii
CHAPTER ONE: INTRODUCTION
1
CHAPTER TWO: LITERATURE REVIEW 2.1 World population and world cereal production
2.2 Stored product insect pests
2.2.1 General information
2.2.2 General biology and life cycle
2.2.2.1 The rice weevil, Sitophilus oryzae (L.) (Curculionoidea:
Dryophthoridae)
2.2.2.2 The red flour beetle, Tribolium castaneum (Herbst)
(Tenebrionoidea: Tenebrionidae)
2.3 Economic importance, damages and impacts of infestation caused by
stored product insects with emphasis on S. oryzae and T. castaneum
2.4 General control of stored product insects
2.4.1 Control of stored product insects using natural products
3 5
7
12
15
17
18
CHAPTER THREE: EFFECTS OF DIFFERENT MEDIUMS IN
THE DEVELOPMENT OF Sitophilus oryzae
(L.) AND Tribolium castaneum (Herbst)
3.1 Introduction
22
iv
3.2 Materials and methods
3.2.1 Stored product insects
3.2.2 Medium preparation
3.2.3 Bioassay
3.2.3.1 Sitophilus oryzae
3.2.3.2 Tribolium castaneum
3.2.4 Proximate Analysis
3.2.5 Susceptibility Index
3.2.6 Data Analysis
3.3 Results
3.3.1 Sitophilus oryzae
3.3.2 Tribolium castaneum
3.4 Discussion
3.4.1 Sitophilus oryzae
3.4.2 Tribolium castaneum
23
23
24
24
26
27
28
28
40
50
53
CHAPTER FOUR: INTRASPECIFIC AND INTERSPECIFIC COMPETITION BETWEEN Sitophilus oryzae (L.) AND Tribolium castaneum (Herbst) AT DIFFERENT DENSITIES
4.1 Introduction
4.2 Materials and methods
4.2.1 Stored product insects
4.2.2 Bioassay
4.2.3 Data Analysis
4.3 Results
4.4 Discussion
57
58
58
59
59
68
CHAPTER FIVE: EVALUATION OF SEVERAL SPICES AS POTENTIAL GRAIN PROTECTANTS AGAINST Sitophilus oryzae (L.) AND Tribolium castaneum (Herbst)
5.1 Introduction
5.2 Materials and methods
5.2.1 Stored product insects
5.2.2 Spices
5.2.3 Rearing medium
72
74
74 75
v
5.2.4 Bioassay
5.2.4.1 Spices in whole form
5.2.4.2 Powdered spices as grain protectants
5.2.4.3 Effects of spices against the development of T. castaneum
immature stages
5.2.4.4 Data analysis
5.3 Results
5.3.1 Insecticidal activity of spices in whole form
5.3.2 Repellency effect of spices in whole form
5.3.3 Powdered spices as grain protectants
5.4 Discussion
5.4.1 Insecticidal activity of spices in whole form
5.4.2 Repellency effect of spices in whole form
5.4.3 Powdered spices as grain protectants
75
75
77
80
82
82
88
91
91
92
CHAPTER SIX: EVALUATION OF SEVERAL EXTRACTS OF SPICES AS CONTACT AND VAPOUR REPELLENTS, AND THE ISOLATION OF EFFECTIVE AND POTENTIAL REPELLING COMPOUNDS IN EXTRACTED MATERIALS OF Elettaria cardamomum (L.) PODS AGAINST Sitophilus oryzae (L.) AND Tribolium castaneum (Herbst)
6.1 Introduction
6.2 Materials and methods
6.2.1 Stored product insects
6.2.2 Spices
6.2.3 Rearing medium
6.2.4 Bioassay
6.2.4.1 Contact repellency assay
6.2.4.2 Vapour repellency assay
6.2.5 Preparation and analysis of Elettaria cardamomum extract
6.2.5.1 Plant materials
6.2.5.2 Thin-Layer Chromatography (TLC)
6.2.5.3 Column Chromatography (CC)
6.2.5.4 Contact repellent assay
95
97
97
98
98
99
99
101
101
102
vi
6.2.5.5 Description of Gas Chromatography/ Mass Spectrum
(GC/MS) method.
6.2.6 Data Analysis
6.3 Results
6.3.1 Spices extraction (Soxhlet extraction method)
6.3.2 Contact repellency assay
6.3.3 Vapour repellency assay
6.3.4 Elettaria cardamomum extract (Thin-Layer Chromatography)
6.3.5 Elettaria cardamomum extract (Column Chromatography)
6.3.6 Contact repellency assay (fractions isolated from Elettaria
cardamomum extracted materials)
6.3.7 Identification of major constituents in E. cardamomum fractions
Gas Chromatography (GC) and Gas Chromatography- Mass
Spectrum (GC-MS)
6.4 Discussion
6.4.1 Spices extraction (Soxhlet extraction method)
6.4.2 Contact and vapour repellency assay
6.4.3 Elettaria cardamomum extracted materials
102
103
103
105
108
114
114
114
118
123
125
126
SUMMARY AND CONCLUSION
130
REFERENCES
134
VITA
APPENDICES
LIST OF PUBLICATIONS AND SEMINARS
vii
LIST OF TABLES
Page
Table 2.1: List of essentials oils (spices/ herbs) previously studied against different stored product insects.
21
Table 3.1: List of eight types of rice grains tested against S. oryzae.
25
Table 3.2: List of six types of flour and two types of starch tested against T. castaneum.
25
Table 3.3: Mean (± S.E.) emergence and mean developmental time of S. oryzae F1 progeny when reared on different rice types at 30.0 ± 0.5ºC and 68 ± 2% RH.
29
Table 3.4: Mean percentage (± S.E.) of new S. oryzae adults emerging from different diets over a period of 73 d at 30.0 ± 0.5ºC and 68 ± 2% RH.
31
Table 3.5: Nutrient composition of various rice types estimated by using proximate analysis.
32
Table 3.6: Mean grain moisture (% ± S.E.) pre- and post-experimental period.
37
Table 3.7: Susceptibility index of each rice type and mean (% ± S.E.) force used to break different types of rice grains.
39
Table 3.8: Proximate composition of various flour/starch.
41
Table 3.9: Mean (± S.E) male and female numbers of T. castaneum reared in a variety of flour/ starches over a period of 140 d at temperatures of 30.0 ± 0.5ºC and 68 ± 2% RH.
46
Table 3.10: Total emergence, mean adult emergence (± S.E.) and developmental time of new T. castaneum adults at temperatures of 30.0 ± 0.5ºC and 68 ± 2% RH in different diets.
48
Table 3.11: The mean (% ± S.E.) of new T. castaneum adults emerging throughout 140 d of the experimental period at temperatures of 30.0 ± 0.5ºC and 68 ± 2% RH in different diets.
49
Table 4.1: Mean (± SE) number of newly emerged adults of S. oryzae and T. castaneum at day 79 when reared separately at different densities.
61
Table 4.2: Mean (± SE) number of newly emerged adults of S. oryzae and T. castaneum at day 79 when reared together at different densities.
63
viii
Table 4.3: Mean (± SE) number of newly emerged adults of S. oryzae and T. castaneum at day 79 when reared together at different densities.
63
Table 4.4: Mean (± SE) number of newly emerged adults of S. oryzae and T. castaneum at day 79 when reared together at different densities.
65
Table 5.1: List of spices and parts used in the screening of effective repellents against S. oryzae and T. castaneum.
76
Table 5.2: Mean mortality of S. oryzae and T. castaneum when exposed to whole forms of five different spices at day 28.
83
Table 5.3: Percentage repellency of T. castaneum and S. oryzae when exposed to substrates treated with 3% (w/w) concentration of powdered spices.
90
Table 5.4: Development failure for immature stages (pupae and larvae) of T. castaneum (in percentage) when reared in substrates treated with 3% (w/w) concentration of powdered spices.
90
Table 6.1: Extracts yield (%) obtained by using Soxhlet extraction on five different types of spices.
104
Table 6.2: Composition of fraction 3Y from extracted materials of E. cardamomum pods.
119
Table 6.3: Composition of fraction 8Y from extracted materials of E. cardamomum pods.
119
Table 6.4: Composition of fraction 1H from extracted materials of E. cardamomum pods.
120
Table 6.5: Composition of fraction 5H from extracted materials of E. cardamomum pods.
121
Table 6.6: Composition of fraction 17H from extracted materials of E. cardamomum pods.
122
Table 6.7: Composition of fraction 34H from extracted materials of E. cardamomum pods.
124
ix
LIST OF FIGURES
Page
Figure 3.1: Total number of adult emergence against different carbohydrate content (%) of diets (r2= 0.71; P < 0.05; y= 8827+92.6x).
33
Figure 3.2: Total number of adult emergence against different ash content (%) of diets (r2= 0.66; P < 0.05; y= 309.7+573.5x).
35
Figure 3.3: Total number of adult emergence against different fibre content (%) of diets (r2= 0.89; P < 0.05; y= 394.4+491.4x).
35
Figure 3.4: Total number of adult emergence against different lipid content (%) of diets (r2= 0.57; P < 0.05; y= 487.6+163.3x).
36
Figure 3.5: Mean weight loss (% ± S.E.) of different rice types caused by S. oryzae infestation over a period of 73 d at 30.0 ± 0.5ºC and 68 ± 2% RH (Tukey’s HSD, P < 0.05).
38
Figure 3.6: Cumulative adult emergence at day 28 against different protein content (%) of diets [r2= 0.97; P < 0.05; y= (-4.68)/(1-2.48e)-(6.68)x]
43
Figure 3.7: Cumulative adult emergence at day 28 against different carbohydrate content (%) of diets [r2= 0.93; P < 0.05; y= (2.65-2.50x)/(1-2.19x+2.82x2)]
43
Figure 3.8: Mean (± S.E.) emergence of emerging adults (± S.E.) reared in different diets on day 28 at temperatures of 30.0 ± 0.5ºC and 68 ± 2% RH (Tukey’s HSD, P < 0.05).
44
Figure 3.9: Mean (± S.E.) emergence of pupae (± S.E.) reared in different diets on day 28 (Tukey’s HSD, P < 0.05) at temperatures of 30.0 ± 0.5ºC and 68 ± 2% RH.
45
Figure 4.1: Mean number of progeny emergences of S. oryzae at different initial densities (r2 =1.00; P< 0.05; y= -4.73+1.51x–1.20x2).
62
Figure 4.2: Mean number of progeny emergences of T. castaneum at different initial densities (r2 =1.00; P< 0.05; y= 5.39+1.63x–1.67x2).
62
Figure 4.3: Mean emerging adults of S. oryzae at (a) 1 pair, (b) 5 pairs and (c) 10 pairs that were reared separately or with T. castaneum at different densities over a period of 79 d.
66
x
Figure 4.4: Mean emerging adults of T. castaneum at (a) 1 pair, (b) 5 pairs and (c) 10 pairs that were reared separately or with S. oryzae at different densities over a period of 79 d.
67
Figure 5.1: Percentage repellency (%) of adult S. oryzae towards whole forms of various spices at day 7 and day 28 (Tukey’s HSD, P < 0.05).
84
Figure 5.2: Percentage repellency (%) of adult S. oryzae towards whole forms of various spices over a 28 day period (Tukey’s HSD, P < 0.05).
86
Figure 5.3: Percentage repellency (%) of adult T. castaneum towards whole forms of various spices at day 7 and day 28 (Tukey’s HSD, P < 0.05).
87
Figure 5.4: Percentage repellency (%) of adult T. castaneum towards whole forms of various spices over a 28 day period (Tukey HSD, P < 0.05).
89
Figure 6.1: Percentage repellency (%) of adult S. oryzae towards methanolic extracts of various spices at different concentrations (Tukey’s HSD, P < 0.05).
106
Figure 6.2: Percentage repellency (%) of adult S. oryzae towards methanolic extracts of various spices at different concentrations (Tukey’s HSD, P < 0.05).
107
Figure 6.3: Percentage repellency (%) of adult T. castaneum towards methanolic extracts of various spices at different concentrations (Tukey’s HSD, P < 0.05).
109
Figure 6.4: Percentage repellency (%) of adult T. castaneum towards hexanic extracts of various spices at different concentrations (Tukey’s HSD, P < 0.05).
110
Figure 6.5: Vapour repellency effect of 50 % (w/w) concentration of methanolic (a) and hexanic (b) spices extracts against S. oryzae at α = 0.05 (Paired t-test).
112
Figure 6.6: Vapour repellency effect of 50% (w/w) concentration of methanolic (a) and hexanic (b) spices extracts against T. castaneum at α = 0.05 (Paired t-test).
113
Figure 6.7: Repellency percentage (%) of isolated fractions from methanolic extracts of E. cardamomum against S. oryzae and T. castaneum.
116
Figure 6.8: Repellency percentage (%) of isolated fractions from 117
xi
hexanic extracts of E. cardamomum against S. oryzae and T. castaneum.
xii
LIST OF PLATES
Page
Plate 2.1: Adult rice weevil, S. oryzae
9
Plate 2.2: Male S. oryzae
9
Plate 2.3: Female S. oryzae
9
Plate 2.4a: S. oryzae larvae (Ventral view)
11
Plate 2.4b: S. oryzae larvae (Side view)
11
Plate 2.5: S. oryzae pupae
11
Plate 2.6: Adult T. castaneum
13
Plate 2.7: T. castaneum larva
13
Plate 2.8: T. castaneum pupa
13
Plate 2.9: Female T. castaneum
14
Plate 2.10: Male T. castaneum
14
Plate 2.11: Terminal view of male and female Tribolium pupae showing the sexual characters (Park 1932).
14
Plate 5.1: Experimental setup for repellency effect of whole forms of spices/ herbs against (a) S. oryzae in rice grains and (b) T. castaneum in rolled oats.
78
Plate 5.2: Experimental setup of treated and untreated areas for repellency effect of powdered forms of spices against (a) S. oryzae in rice grains and (b) T. castaneum in wheat flour.
79
Plate 5.3: Experimental setup of developmental of T. castaneum when reared in rearing medium previously treated with powdered spices (10% w/w).
81
Plate 6.1: Experimental setup for contact repellency assay using filter-paper impregnation method against S. oryzae and T. castaneum.
100
Plate 6.2: Experimental setup for fumigant repellency assay using filter-paper impregnation method against S. oryzae and T. castaneum.
100
Plate 6.3: TLC plates under long UV (a), short UV (b), and 5% sulphuric acid spot test (c) for hexanic extracts of E. cardamomum.
115
xiii
Plate 6.4: TLC plates under long UV (a), short UV (b), and 5% sulphuric acid spot test (c) methanolic extracts of E. cardamomum.
115
xiv
LIST OF ABBREVIATIONS
gm grams
mg milligrams
ml millilitres
µl microliters
RH relative humidity
S. E. Standard Error
m meter
cm centimeters
mm millimeters
° C degree Celcius
min minutes()
h hour
d day
wk week
N Newton
SI susceptibility index
PR Percentage Repellency
ODW Overall dried weight
TLC Thin-Layer Chromatography
CC Column Chromatography
GC/MS Gas Chromatography/ Mass Spectrum
xv
PERKEMBANGAN DAN PERSAINGAN DALAM KUMBANG BERAS,
Sitophilus oryzae (L.) DAN KUMBANG TEPUNG, Tribolium castaneum
(Herbst), DAN RESPONS MEREKA TERHADAP KOMPAUN AKTIF DI
DALAM REMPAH TERPILIH.
ABSTRAK
Serangga hasil simpanan menyebabkan lebih daripada 20% jumlah kerosakan
pada hasil simpanan di negara membangun dan lebih daripada 9% jumlah kerosakan
di negara-negara maju setiap tahun. Keselamatan makanan adalah terancam
terutamanya dengan peningkatan pesat dalam populasi dunia. Tesis ini bertumpu
pada aspek kelakuan dan kawalan Sitophilus oryzae (L.) dan Tribolium castaneum
(Herbst). Keduanya adalah antara dua serangga hasil simpanan yang paling biasa
menyerang hasil simpanan di negara tropika. Satu kajian mengenai kadar
perkembangan serangga ini di dalam medium yang berbeza telah dijalankan.
Sitophilus oryzae didedahkan kepada beras perang, beras tempatan, beras parboiled,
beras calrose, beras basmathi, beras merah, beras pulut hitam, dan beras wangi.
Kumbang-kumbang tersebut lebih suka medium dengan kandungan karbohidrat yang
lebih rendah tetapi kandungan abu dan serat yang lebih tinggi. Lapan jenis tepung
dan kanji (tepung atta, tepung gandum, tepung naik sendiri, tepung beras, tepung
kastard, tepung jagung, kanji ubi kayu, dan kanji kentang) digunakan untuk membela
T. castaneum dan kumbang -kumbang itu membesar dengan baik di dalam medium
yang mengandungi kandungan protein yang lebih tinggi, manakala kandungan
karbohidrat yang tinggi memudaratkan perkembangan mereka. Persaingan intra- dan
inter- spesies adalah bergantung kepada ketumpatan populasi permulaan. Dalam
kajian intraspesies, fekunditi S. oryzae and T. castaneum berkurang apabila di atas
xvi
dan di bawah ketumpatan populasi permulaan yang tertentu. Walau bagaimanapun,
kajian interspesies mununjukkan bahawa peningkatan ke atas ketumpatan permulaan
T. castaneum menyebabkan kesan negatif yang beransur-ansur ke atas perkembangan
progeni S. oryzae tetapi tidak memberi kesan sebaliknya. Kedua-dua jenis serangga
didedahkan kepada lima jenis rempah (Elettaria cardamomum (L.), Brassica nigra
(L.), Rosmarinus officinalis L., Capsicum frutescens L., dan Cassia auriculata L.)
dalam kedua-dua bentuk seluruh dan serbuk. Walaupun kadar kematian yang
direkodkan tidak tinggi apabila serangga tersebut didedahkan kepada rempah dalam
bentuk asal, tetapi S. oryzae didapati lebih lemah berbanding dengan T. castaneum.
Di antara rempah yang diuji, E. cardamomum dalam bentuk serbuk adalah paling
berkesan terhadap kedua-dua spesies serangga. Akhirnya, kajian untuk
mengenalpasti kesan repelensi bahan ekstrak rempah terhadap serangga dijalankan.
Elettaria cardamomum sekali lagi merupakan calon repelensi yang terbaik.
Kehadiran hidrokarbon aromatik, ester, asid ester, asid karbosilik serta beberapa
kompaun yang tidak diketahui mungkin menyumbang kepada ciri repelensi rempah
tersebut.
xvii
DEVELOPMENT AND COMPETITION IN RICE WEEVIL, Sitophilus oryzae
(L.) AND RED FLOUR BEETLE, Tribolium castaneum (Herbst), AND THEIR
RESPONSES TO ACTIVE COMPOUNDS IN SELECTED SPICES.
ABSTRACT
Stored product insects causes more than 20 % in total damages to stored
products in developing countries and 9 % in total damages to stored products in
developed countries on a yearly basis. Food security is threatened especially with the
rapid increase in world population. This thesis focuses on the behavioural and control
aspects of Sitophilus oryzae (L.) and Tribolium castaneum (Herbst). Both are two of
the most common stored products insect attacking stored products in tropical
countries. A study on the insects’ development rates in different mediums were
carried out. Sitophilus oryzae were exposed to unpolished brown rice, local polished
rice, parboiled rice, calrose rice basmati rice, red rice, black glutinous rice and
fragrant polished rice. The weevils preferred mediums with lower carbohydrate
contents but higher contents of ash and fibre. Eight types of flour and starch (atta
flour, enriched wheat flour, self-rising flour, rice flour, custard powder flour, corn
flour, tapioca starch, and potato starch) were used to rear T. castaneum and the
beetles developed well in mediums with higher protein contents, while high
carbohydrate contents were detrimental to their development. Competition between
and within the species is dependent on the initial population density. In the
intraspecific study, the fecundity of S. oryzae and T. castaneum was reduced above
and below a certain initial population density. However, the interspecific study
showed that an increase in initial density of T. castaneum has a gradual negative
impact on the progeny development of S. oryzae but no effect vice versa. Both insect
xviii
species were exposed to five spices (Elettaria cardamomum (L.), Brassica nigra (L.),
Rosmarinus officinalis L., Capsicum frutescens L., and Cassia auriculata L.) in both
whole and powdered form. Although high mortality was not recorded when the
insects were exposed to the whole formed spices, but S. oryzae was more susceptible
than T. castaneum. Among the spices tested, the powdered form of E. cardamomum
was most effective against both insect species. Finally, a study to determine the
repellency effects of extracted materials from the spices against the test insects was
carried out. Elettaria cardamomum was again found as the best repellent candidate.
The presence of aromatic hydrocarbons, esters, acid esters, carboxylic acids as well
as some unknown compounds may have attributed to the repellent property of the
spice.
1
CHAPTER ONE
GENERAL INTRODUCTION
About 80% of the food consumed by humans comes from grains (Pimental
and Pimental 2008). Pimental (1997) stated that about 40% of world crop losses are
attributable to infestation by pests. Insects are the main cause of grain loss (Gwinner
et al. 1996) accounting to 15% of the total world crop losses (Pimental 1997). Gomez
(2004) stated that the food industry at all levels suffer losses due to pest insects
infestation. It is reported that the increase in pest numbers is largely dependent on the
type of species that is attacking the product (Aulakh and Regmi 2013) and most of
the damages caused by insect pests are results of direct feeding (Santos et al. 1990).
Post-harvest insect pests can be classified into primary pests which attack
sound grains, while secondary insect pests infest damaged or broken grains. Grains
previously damaged by pre-harvest pests and by primary storage pests enable easier
access by secondary pests. Moreover, processed storage products are also susceptible
to secondary pest attacks (Rees 2004). Coleoptera (beetles) is one of the main groups
of insects that are of economic importance as post-harvest insect pests. Both the
larvae and adult stages are destructive and the main culprit for damaging stored
products (Sallam 2004).
Buzby and Hyman (2012) stated that food losses can be quantitative,
qualitative or both. Quantitative loss refers to a loss in products’ weight, while
qualitative loss implies a reduction in nutrient value as well as changes to taste,
colour, texture or presence of unwanted residues such as insect fragments and frass,
and contamination by fungi of the stored product. Consequently, the values of the
damaged grains to be sold, consumed or planted will be reduced (Sallam 2004).
2
A lot of contentions and assumptions over the scale of post-harvest losses,
especially damages caused by insects have been made. The continuous increase in
world population results in more people to feed, thus a decrease in such losses is vital
and can assist in increasing the accessibility of food supply, especially to people in
developing countries (Boxall 2001). The phasing-out and subsequent ban of methyl
bromide used previously to manage stored product pest insects population has caused
a worldwide search for other alternatives (Fields and White 2002). In developing
countries such as Malaysia, the phasing out was scheduled in January 2015 (UNEP
2014). Over the years, the demand for novel control methods has intensified as
concerns of the effects of control measures towards human health and the
environment are surfacing (Mahdi and Rahman 2008).
Therefore, the objectives of this study were;
1. To determine the effects of different mediums on the development of Sitophilus
oryzae (L.) and Tribolium castaneum (Herbst).
2. To study the effects of population density on the intra- and inter-species
competition of S. oryzae and T. castaneum.
3. To evaluate the potential of several spices as grain protectants against S. oryzae
and T. castaneum.
4. To ascertain the contact and vapour repellent effect of extracted materials from
several spices against S. oryzae and T. castaneum and isolation of effective and
potential repelling compounds from the spice, Elettaria cardamomum (L.).
3
CHAPTER TWO
LITERATURE REVIEW
2.1 World population and world cereal production
In the year 2010, the world population was recorded at 6.9 billion, a 34
percent increase from 2.5 billion in 1950. The world population has grown with an
annual rate of 1.1 to 1.2 percent which is about 78 million people per year from 2005
to 2010 (UN 2010). It is estimated that by the year 2050, the world population would
reach 10.5 billion (UN 2013). According to the Population Reference Bureau (2012),
less developed countries are more likely to have a greater increase in population
growth. Therefore, most of the food demands would have come from those in poor
parts of the world which is an additional 33 % of the current total world population.
Throughout the years, the upsurge in human population has urged for
additional food supply which puts exceptional pressure on the food production
industry (Evans 2009, Godfray et al. 2010) which calls for 60 % increase to sustain
the food demand in 2050 (Alexandratos and Bruinsma 2012). In 2006, more than 87
percent of the total worldwide grain production consists of maize, wheat and rice
(FAO 2006). The world’s cereal production was recorded at about 2.475 billion
tonnes in 2013 with world production of rice amounting to 745 million tonnes and
wheat production at 711 million tonnes (FAO 2013). Nevertheless, food production
as well as the distribution systems may not be or are still not sufficient to feed the
ever increasing world population which can subsequently lead to food insecurities
(FAO 1999). Therefore, the rise in worldwide demand for food is expected for at
least another 40 years with the constant increase in population and food intake
(Godfray et al. 2010). According to the UN (2001), an average of 2900 kcal per day
is required by an adult person for their daily activities. It was reported that an
4
average food of 3500 kcal/day is consumed by people in developed countries, while
those in poor countries obtain 2000 kcal/day or less, causing incidents of
malnourishment. Gilland (2002) stated that food production in the world can supply
about 2800 kcal/day per capita and this amount is just about enough to sustain the
world population but only if the statistics and calculations are accurate. It is also
important to take into account livestock consumption that is recorded at 75 percent of
the world cereal production (Alexandratos 1999, Gilland 2002).
The current food crisis situation is reportedly to be extremely alarming given
the statistics. It was estimated that in 2010, 925 million people were still
undernourished which amounts to approximately 16% of the total population in
developing countries (FAO 2010). More recently, FAO (2012) reported that from
year 2010 to 2012, around 12.5% of the world population (870 million people)
suffers from malnutrition. Carvalho (2006) stated that the divergence between world
food production and human population is expected to intensify until the year 2050.
FAO (1999) reported that besides economic and political attributes,
environmental factors play a considerable role in upsetting the production of food
crops around the world, especially in impoverished places. Agricultural lands are
cleared to allow cultivation of plants for biofuels production and to construct housing
to accommodate the growing population (Godfray et al. 2010). Crop production is
also influenced by the change in climate, where rainfall pattern and temperatures can
change the growing season of food crops. Moreover, food crops become more
susceptible to pest attacks and diseases. This subsequently disrupts the food
production system and also threatens food security (Gregory and Ingram 2000,
Gregory et al. 2005, Parry et al. 2005).
Therefore, currently much effort is needed for more food yield and ensure
5
food security to cutback poverty, malnutrition and improve human health and
welfare (Carvalho 2006). It is essential to reduce post-harvest losses to maintain
future global food security (Alexandratos and Bruinsma 2012). This is required to be
carried out in an environmentally and socially sustainable way and one of the major
challenges is to revise the approach in producing, storing, processing, distributing
and accessing food (Godfray et al. 2010).
2.2 Stored product insect pests 2.2.1 General information
Stored products are materials in a dried form, such as cereals, pulses, dried
seeds and root crops, which enables them to be stored for use at other times. One of
the major causes for the drop in stored products’ quality in places with hot and humid
weather is due to the infestation by insects (Chomchalow 2003). Stored product
insects have long been associated with human activities dating back to ancient
Egyptian times (Rees 2004). A number of stored pests found in the late 20th century
have even been reported to be uncovered from the tombs of the pharaohs (Levinson
and Levinson 1998). Although many of the pests were initially limited in their
distribution, activities of trading over thousands of years have caused them to
disperse and spread throughout the world (Rees 2004). Moreover, their
morphological, physiological and behavioural adaptations made worldwide
infestations possible (Freeman 1973).
According to Rajendran (2002), more than 600 species of beetles and 70
species of moths, 355 species of mites, 40 species of rodents and 150 species of fungi
have been recorded and identified to be related to the many types of stored products
in existence. The insect pests of stored products have been identified to come mainly
6
from three orders; Coleoptera (beetles), Lepidoptera (moths) and Psocoptera (psocids
or booklice) (Rees 2004). Beetles can be categorized into about 110 to 115 families
and amongst them, five of the families comprise of more than 20,000 species
(Hedges and Lacey 1996). Although beetles are considered beneficial to the
environment, some beetles are also pests of crops and stored products (Cramer 2006).
Chomchalow (2003) reported that a substantial loss in terms of physical and
nutritional value have been reported to be caused by weevils, bruchids and other
insects, while Herbert (2009) stated that the main insect pests found to attack or
infest stored products were reported to be the lesser grain borer, rice weevils, maize
weevils, cadelle beetles, flat grain beetles, rusty grain beetles, sawtoothed grain
beetles, foreign grain beetles, mealworm beetles, red flour beetles, confused flour
beetles, Indian meal moths, and book lice.
Food security and household incomes can be greatly affected when storage
insects cause severe losses to storage products (Belmain and Stevenson 2001,
Chomchalow 2003). Besides that, it also causes damaging effects to the economy
(Chomchalow 2003). Stored products insect can adjust to food handling processes
and storing conditions as these insects have the ability to infest different types of
food instead of just one or several food types. Moreover, they can tolerate a broader
range of temperature and relative humidity in addition to having relatively long
reproduction periods. Some stored product insects can also survive without food for
long periods and because of their small size, large populations would have been
established before they are detected (Cox and Collins 2002).
Insect pests of stored products can be categorized either as commodity
feeders, fungal feeders, predators, parasitoids, foragers and accidentals, or
scavengers. Insects that feed directly on the commodity are either primary or
7
secondary pests (Rees 2004). Those that fall into the category of primary pests are
internal feeders of kernels that penetrate and feed on commodities that are
undamaged and intact (Philips and Throne 2009) or spend a significant amount of
time developing within the grain (Mason 2003). On the other hand, secondary pests
are external feeders that require the commodity to be damaged or processed (e.g.
milled grains and grain-based food products) before they can attack or feed on the
broken and fine materials of the commodity (Mason 2003, Rees, 2004, Philips and
Throne 2009). Products previously damaged by other pests, mainly by primary pests
or products which have been subjected to poor threshing, drying and handling also
risks being attacked by secondary pests. These pests are known to attack a wider
range of food products than compared to primary pest species (Semple et al. 1992).
Meanwhile, storage insects classified as fungal feeders are those that feed on mould
and mould spores which give extra nutrients that may not be present from direct
feeding of the commodity. Other stored product insects can act as predators by
preying on other insects present in the commodity. Parasitoids such as wasps that
attack stored product insects can also be a pest itself when present in the commodity.
Moreover, stored products may also contain occasional insects categorized as
foragers or accidentals such as cockroaches and ants. Some stored product insect
pests are also scavengers which include insects that feed on dead insects and other
dried material of animal origin (Rees 2004).
2.2.2 General biology and life cycle 2.2.2.1 The rice weevil, Sitophilus oryzae (L.) (Curculionoidea: Dryophthoridae) Sitophilus oryzae is a primary pest (Rees 2004) and one of the most common
pests that cause both quantitative and qualitative losses to stored grains (Park et al.
2003). In warm tropical countries, S. oryzae is the main insect pest infesting stored
8
products (Batta 2004). Longstaff (1981a) reported that processed animal foods are
also attacked by S. oryzae but will only reproduce in whole grains with moisture
levels ranging from 10 to 16%. Adult S. oryzae are less limited in their diets as the
larvae need to develop within grains that are intact even though both adult and larval
stages feed on the same foods (White and Leesch 1995).
Measuring from 2.3 to 3.5 mm in length, adult weevils are small with a stout
appearance (Plate 2.1). Its forewings have been modified to become hard and
protective, known as elytra and are dark-reddish brown in colour with four light-
coloured patches (Koehler 1994, Walker 2008). The S. oryzae adult has a head which
is elongated into a snout where the mouthparts are located (Mason 2003). The snout
is as long as the prothorax or the elytra (Koehler 1994) and each adult weevil possess
a pair of elbowed antenna (Canadian Grain Commission 2009). Male and female
weevils are discerned by the appearance of their snouts. The snout in male weevils is
shorter and wider with heavy irregular pitting (Plate 2.2) while female snouts are
relatively long and narrow with light regular pitting (Plate 2.3) (Halstead 1963, Rees
2004, Walker 2008b).
Shortly after emerging from kernels, observations showed that adult weevils
will begin mating (Singh and Soderstrom 1963). Female weevils will make a small
hole (feeding puncture) in a grain kernel and deposits an egg in it (Longstaff 1981a,
Rees 2001). The egg is protected when the hole is sealed with a waxy secretion
(Longstaff 1981a, Canadian Grain Commission 2009). Campbell (2002) stated that
not all holes made by female weevils are deposited with eggs as some grains are left
void or becomes their food source. A single female weevil can lay approximately
150 eggs throughout its lifespan (Canadian Grain Commission 2009) and these eggs
9
Plate 2.1: Adult rice weevil, S. oryzae.
Plate 2.2: Male S. oryzae.
Plate 2.3: Female S. oryzae.
10
will hatch into larvae with a short and stout ‘C’ shape. Larvae of S. oryzae are white
or cream in colour with a dark head capsule, legless (Plate 2.4a, 2.4b) and develop
inside whole grain kernels (Koehler 1994, Mason 2003). The kernel in which it
hatches in will ultimately be hollowed out by the chewing action of the larva as it
feeds on it (Alfonso-Rubí et al. 2003). Longstaff (1981a) reported that a single grain
may contain more than one egg, which can result in the development of more than
one larva. However, cannibalistic behaviours are exhibited by S. oryzae larvae if they
come across other larvae that are less developed thus making it unlikely for more
than one larva to survive, pupate and progress into the adult stage (Danho et al. 2002,
Arbogast 1991). After the pupa (Plate 2.5) emerges into an adult weevil, it will stay
within the grain for a few days to enable the hardening and darkening of the cuticle
layer (Longstaff 1981a). Adult S. oryzae will retract their legs towards their body
when disturbed and remain motionless to appear dead (Koehler 1994).
The development of S. oryzae eggs to pupae can take up to 25 days or more
under warm conditions. According to Koehler (1994), the life cycle of S. oryzae is
completed in 5 to 8 weeks under optimal temperatures (between 27°C and 31°C), the
shortest being 25 days at 27°C and 70% RH, while Singh et al. (1974) reported that
30°C and 75% RH is the optimal development conditions for S. oryzae. At 27±1°C
and 69 ± 3% RH, Sharifi and Mills (1971) reported that a longer average time for the
complete development of S. oryzae is recorded at around 37 d (range 33-49d). If
temperatures drop lower than 17°C, their development will stop (Koehler 1994).
Adult weevils are long-lived with a life span that can range from 3 to 6 months (Rees
2004).
11
Plate 2.4a: S. oryzae larvae (Ventral view) Plate 2.4b: S. oryzae larvae (Side view)
Plate 2.5: S. oryzae pupae
12
2.2.2.2 The red flour beetle, Tribolium castaneum (Herbst) (Tenebrionoidea:
Tenebrionidae
Tribolium castaneum is mostly encountered in tropical places and they are
often the coloniser of a stored commodity (Rees 2004). The adults are reddish-brown
(2.6-4.4 mm) with a pair of antennae that ends with a conspicuous three-segmented
club (Plate 2.6) (Bousquet 1990, Rees 2004). This insect species can live for a year
(Howe 1962) or more and in some cases for as long as three years as reported by
Baldwin and Fasulo (2003). Adult T. castaneum females lay white, small and
cylindrical eggs amongst food products. They can lay 11 eggs daily at an optimum
temperature of 32.5°C and during their entire existence up to 1000 eggs can be laid
(Howe 1962, Rees 2004). Larvae possess a pale brown head and their last abdominal
segment comprises of a pair of dark upturned and pointed structures (Plate 2.7) (Hill
1975). They are of elateriform, active (Rees 2004) and will remain inside grains
while waiting to pupate (Howe 1962, Hill 1975). This insect species spends most of
its developmental time (60%) in the larval form (Rees 2004). The pupa is exposed as
it is not enclosed in a cocoon or a case (Mason 2003) and can be yellowish white to
brown in colour (Plate 2.8) (Hill 1975). At the pupal stage, male and female T.
castaneum can be easily set apart by examining the genital papillae which is located
at the anterior to the urogomphi. The urogomphi is a pair of pointed structure found
at the end of each pupa. The genital papillae in female pupae are of finger-like
structures and bigger (Plate 2.9) than compared to those of the male pupae which
look like fingertips instead of fingers (Plate 2.10) (Beeman et al. 2009).
Under different conditions (temperature and relative humidity) the
developmental period of T. castaneum can be different. At 30°C, a full life cycle can
be completed in 35 days (Hill 1975). When reared in between 20ºC to 37.5ºC, and at
13
Plate 2.6: Adult T. castaneum
Plate 2.7: T. castaneum larva
Plate 2.8: T. castaneum pupa
14
Plate 2.9: Female T. castaneum
Plate 2.10: Male T. castaneum
Plate 2.11: Terminal view of male and female Tribolium pupae showing the sexual characters (Park 1932).
15
a relative humidity greater than 70%, a complete life cycle only takes 19 to 20d
(Howe 1956). Rees (2001) stated that under optimum conditions of 35°C and 75%
RH, the life cycle of T. castaneum takes around 20 d.
2.3 Economic importance, damages and impacts of infestation caused by stored
product insects with emphasis on S. oryzae and T. castaneum
Harvested products are usually stored for many reasons including providing a
continuous supply of food and feed that can last all year round as well as kept for
future planting and sold off when market prices for the particular product is high to
acquire more earnings (Demissie et al. 2008). However, storage of products also
comes with its consequences as post-harvested products are more susceptible to
infestation and damages by stored product insect pests (Rees 2004). Infestation of
stored product by insects causes various damages and economic losses. Mpuchane
and Siame (1998) stated that with the lack in post-harvest handling procedures, the
contamination of food commodities are made worse. Although direct consumption of
raw commodities is most common, ingredients and finished products are also
attacked (Mason 2003). An estimated 9% of postharvest losses in developed
countries and 20% or higher in losses in developing countries were reported to be
caused by stored product insects (Philips and Throne 2010). It was reported that total
post-harvest losses of crops were accounted at 40% in hot and humid regions while
drier regions recorded more than 10% in losses (Appert 1987).
When the quantity and quality of grains are affected, this renders the
retraction of products, risks possible discontinued businesses (Cramer 2006) and
requires the party at fault to bear the ensuing social and legal costs (Rees 2004).
Expenses in control efforts as well as attempts to inhibit further infestations are also
16
increased, while the labour and hardwork that goes into cultivating, managing,
manufacturing and storing commodities are made futile with infestation problems
(Rees 2004). In the food industry, the presence of arthropod pests should not be
taken lightly as some insects can transmit disease-causing bacteria (Olsen 1998b,
Foil and Gorham 2000). Individuals who are prone to allergies may develop
hypersensitivity towards body parts of insects or waste products such as cast skins,
excretory products, and pheromones secreted (Olsen 1998). These by-products will
also taint the tastes of food products (Mason 2003). In addition, an increase in
commodity moisture levels during and throughout the insect infestation will
encourage mould growth (FAO 1985, Rees 2004) and damages to seed embryo by
insects will reduce the germination rate of grain seeds (FAO 1985).
Sitophilus spp. attacks whole cereal grains, solid cereal products as well as
some pulses (Rees 2004). Each year massive damages are caused by S. oryzae to
stored cereal grains and products which accounts for hundreds of millions in losses
(Reddy 1950). Amongst the locally produced grains, rice in the unhusked form
(paddy) and milled form is of utmost concern in Malaysia. These grains are either
stored for a short or an extended period of time in different forms and under different
conditions (Muda 1985). Several researches have recorded around 40 insect species
in Malaysia that attacks stored paddy and rice (Singh 1972, Yunus 1980, Lim et al.
1980, Rahim et al. 1983) with S. oryzae as the main species (Rahim 1985). This
insect species is a prolific breeder, producing a lot of progeny (Rees 2004). Their
infestation not only reduces grains into powder and causes a buildup of heat and
moisture in the product (Longstaff 1981a, Kučerová 2002), but the presence of their
frass also contaminates the grains (Longstaff 1981a). In a storage area, the presence
of S. oryzae is mostly due to the relocation of rice stocks (Rahim 1985). Moreover,
17
since S. oryzae is capable of flight (Mason 2003), these weevils can infest grains
stored at far ends of warehouses (White and Leesch 1995).
Tribolium castaneum is commonly found in flour mills, warehouses, retail
stores (Campbell and Runnion 2003) and food-processing facilities (Mills and
Pedersen 1990). In Malaysia, this species is one of the main secondary insect species
found in significant numbers in warehouses and other storage facilities (Rahim 1985).
This species can infest a wide variety of stored grain products such as flour, cereals,
crackers, beans, spices, pasta, cake mix, dried pet food, dried flowers, chocolate, nuts,
seeds, and even dried museum specimens (Via 1999, Weston and Rattlingourd 2000).
They prefer damaged grains but can also attack intact grains especially if the
moisture content is high (Bousquet 1990). According to Smith el al. (1971), bread
made from contaminated flour which was previously infested with Tribolium spp.
has been reported to give a bad taste when consumed. A heavy infestation with this
insect species will give flour and other food products a grayish tint which can
encourage mould growth and make the products unsuitable for use or consumption
(Mason 2003). Thirteen types of quinines have been identified (Howard 1987) from
the abdominal glands of T. castaneum which gives a foul smell to food products
(Rees 2004) These chemicals have been reported to cause jaundice, anaemia,
haemoglobinuria and cachexia in humans (Omaye et al. 1981) as well as allergic
reactions (Alanko et al. 2000).
2.4 General control of stored product insects
The infestations of insects and their management methods vary (Lim 1988)
and entomologists around the world have long attempted to successfully control
stored product insects (Salem et al. 2007), where gaseous, synthetic fumigants and
18
residual insecticides are primarily used in controlling their population (Chomchalow
2003). In developed countries, the use of synthetic pesticides is the main method to
protect crops against pests (Fields 2006) and have been applied at a large scale
against stored product insect pests in grain storage facilities since the 1950s (Bond
1984). Active ingredients such as deltamethrin, cypermethrin, permethrin and
fenvalerate were effective as grain protectants, as sprays on packaging materials and
construction materials for warehouses against Sitophilus zeamais Motsch., T.
castaneum, Rhyzopertha dominica (F.), Callosobruchus chinensis (L.) and
Callosobruchus maculatus (F.) (Ceballo and Morallo-Rejesus 1986). Insect growth
regulators (IGRs) were also tested and were found to be effective with some insects
(Ephestia cautella (Walker) (Madlanyangbayan and Morallo-Rejesus 1986), Corcyra
cephalonica (Stainton) (Marbida 1986) and Plodia interpunctella (Hubner) (Fajardo
and Morallo-Rejesus 1980). Non-chemical methods such as using low or high
temperature, low moisture grain, diatomaceous earth, hermetic storage, impact and
varietal resistance were also practiced to curb insect infestation (Fields 2006).
2.4.1 Control of stored product insects using natural products
Today, the control of stored product insect pests demands novel control
methods as there are elevated concerns over the deposits of insecticide in processed
cereal products, insects developing resistance towards insecticides, higher expenses
of insecticide application, and the potential environmental impacts (Aslam et al. 200,
Udo 2005, Fields 2006, Salem et al. 2007, Mahdi and Rahman 2008). The search for
alternatives has been further intensified with the worldwide phasing out and ban on
methyl bromide, a fumigant insecticide effective for killing postharvest insects
(Fields and White 2002).
Chomchalow (2003) advised technologists and scientists to develop control
19
practices that are simple and economic as it is vital to reduce unnecessary wasting of
stored products in farms and farm storage areas. Moreover, Udo (2005) suggests the
need to find organic sources that are easily obtainable, inexpensive, and harmless to
animals and the environment. Even without using chemical alternatives, various
prevention and control methods that are nontoxic, efficient and simple can be used to
control stored-product insect pest populations (Philips and Throne 2010). In recent
years, the management of stored product pests focuses on the use of materials of
natural origin (Nadra 2006). Scarcely any attention was given in search for plant-
based insecticides and repellents as well as determining the efficacy of traditional
methods after the discovery of synthetic products (Curtis 1990). Moore et al. (2007)
stated that collectively, substances of natural sources do not pose any threat or put
consumers at risk as many phytochemicals possess pharmacology properties.
Currently, the use of phytochemicals is gaining popularity as the public consider
these products to be better as they derive from natural sources (Gerberg and Novak
2007).
Garland (2004) stated that over the years, many researches propose the use of
different plants as insecticides that gave very promising results. Botanical sources for
example, spices, medicinal and other plants are amongst the many different materials
used as protectants of stored products from pests (Chomchalow 2003). According to
Liu et al. (2006) and Isman (2006), the use of natural products such as plant extracts
are beneficial as they can be target species specific, are locally available, less
persistent in the environment and usually possess distinctive modes of action with
low mammalian or ecotoxicity. Emeasor et al. (2005) and Nadra (2006) reported that
certain oils and extracts of plants as well as the powdered form are highly effective in
controlling stored product insects as the constituents of the plants caused high
20
mortality and suppressed the reproduction rate. Moreover, plant products have been
found to repel or attract insect pests (Mohan and Fields 2002), where essential oils,
powders or distillates have been found to show promise in repelling stored product
pests from grains and acts as feeding and oviposition deterrents (Adler et al. 2000).
These plant extracts and essential oils show promise in protecting crops as they
contain monoterpenoids, diterpenoids, sesquiterpenoids and other compounds that
show ovicidal, larvicidal, repellent, deterrent, antifeedant and toxic effects in a wide
range of insects (Fields et al. 2001, Pungitore et al. 2003, Boeke et al. 2004, Liu et al.
2006, Isman 2000, 2006).
Plants used for the purpose of biocides development should be easy to grow
and plentiful to ensure continuous supply. Besides that, plant parts that show
potential repellent activities should be from replaceable parts of the plant, for
example the leaves or seeds (Belmain and Stevenson 2001). The production of plant-
based compounds that are of top quality may be extremely costly especially when the
amount of bioactive compounds obtained is low. Therefore, it is essential that plant
extraction methods utilized be uncomplicated (Moore et al. 2007).
Protection of stored products can be achieved with the application of plants,
plant parts or extracts that exhibits repellent or toxic properties (Adler et al. 2000).
Spices are plant products that can be used to control stored product insects as they
are inexpensive, readily obtainable and less toxic (Aslam et al. 2002, Mahdi and
Rahman 2008). Spices refers to plant parts used to flavour food which consists of
dried seed, fruit, root, bark or vegetative parts of a plant that is used in small
quantities (Boning 2010, Mahdi and Rahman 2008). They have many other uses
which include preserving food, as medicine, in religious rituals such as incense, as
21
cosmetics, for the perfume industry and even as vegetables (Mahdi and Rahman
2008).
Table 2.1 shows a list of some of the many essential oils (spices/ herbs) tested
by numerous researchers against different stored product insects.
Table 2.1: List of essentials oils (spices/ herbs) previously studied against different stored product insects. Plant name Insect species References Syzygium aromaticum (L.) T. castaneum;
Sitophilus zeamais Motsch. Ho et al. (1994)
Illicium verum Hook T. castaneum; S. zeamais
Ho et al. (1995)
Myristica fragrans Houtt. T. castaneum; S. zeamais
Huang et al. (1997)
Artemisia annua T. castaneum; Callosobruchus maculatus (L.).
Tripathi et al. (2000)
Pimpinella anisum L.; Cuminum cyminum L.; Eucalyptus camaldulensis L.; Origanum syriacum var. bevanii (Holmes); Rosmarinus officinalis L.
Tribolium confusum du Val; Ephestia kuehniella (Zell.)
Tunç et al. (2000)
Elettaria cardamomum (L.) T. castaneum; S. zeamais
Huang and Ho (2000)
Curcuma longa L. R. dominica; S. oryzae; T. castaneum
Tripathi et al. (2002)
Cinnamomum zeylanicum L.; Etlingera elatior (Jack); Etlingera pyramidosphaera (K.Schum.); Zingiber officinale Rosc.; C. longa; Piper nigrum L.; Cymbopogon citratus L.; Capsicum annuum L.
S. zeamais Ishii et al. (2010)
Origanum onites L.; Satureja thymbra L.; Myrtus communis L.
Ephestia kuehniella Zeller; Plodia interpunctella Hübner; Acanthoscelides obtectus Say
Ayvaz et al. (2010)
Alpinia conchigera Griff; Zingiber zerrumbet Smitt.; Curcuma zedoria (Berg.)
T. castaneum; S. zeamais
Suthisut et al. (2011)
Elettaria cardamomum (L.)
C. maculatus; T. castaneum; Ephestia kuehniella Zeller
Abbasipour et al. (2011)
22
CHAPTER THREE
EFFECTS OF DIFFERENT MEDIUMS IN THE DEVELOPMENT OF
Sitophilus oryzae (L.) AND Tribolium castaneum (Herbst)2
3.1 INTRODUCTION
Population growth in stored-product insects are dependent on the food which
they consume (Inouye and Lerner 1965). According to Ziegler (1976), the
oviposition rate and emergence of new adults are very much dependent on the quality
and type of the substrate.
It is known that the main diet of storage pest consists of stored grains (Irshad
et al. 1988). However, certain grains or stored products are more prone to insect
infestation, while others are less susceptible to attacks. Previous studies have been
conducted to evaluate the food preferences for stored product insects in an attempt to
ascertain diets that are suitable for their growth and development (Verner 1971).
Studies by Baker (1975) found that the development of Sitophilus oryzae larvae were
improved when the minerals and vitamins supplied by dietary brewer's yeast and
wheat germ were replaced with mineral and vitamin mixtures. Certain amino acids
were also found to be required for the growth and development of S. oryzae larvae
(Baker, 1978). Campbell and Runnion (2003) stated that different types of flour have
different nutrient constituents and the development of Tribolium castaneum is
considerably affected when there is a slight difference in quality. Tribolium
castaneum did not survive when reared on cornmeal (Sokoloff et al. 1965) and their
performance was low when reared in white wheat, brown rice and rice, but the
addition of yeast improved their development (Sokoloff et al. 1965). Inouye and
2 Published in Journal of Economic Entomology 104(6): 2087-2094, Relationship between population growth of the red flour beetle, Tribolium castaneum and protein and carbohydrate content in flour and starch; impact factor 1.506.
23
Lerner (1965) suggested studies on the nutritional requirements of Tribolium to be
carried out in order to understand the nature of their competitive ability.
This study was initiated to understand the nutrient requirements for the
development and growth of S. oryzae when exposed to different rice types as well as
investigate the influence of different diets on the performance of T. castaneum. It is
hypothesized that the development time for S. oryzae and T. castaneum on different
diets may be related to the nutritional contents of the diet. The damages that these
insects can cause to a particular amount of products over a certain period of time are
vital in an attempt to ascertain the extent of damages these insects can instigate.
Therefore, information regarding the population growth in S. oryzae and T.
castaneum when presented with these diets may be useful in constructing suitable
management approaches in an effort to reduce infestations in grain storages.
3.2 MATERIAL AND METHODS
3.2.1 Stored product insects
Adults of S. oryzae and T. castaneum were collected from subcultures
previously reared from the original stock cultures in the Urban Entomology
Laboratory, Vector Control Research Unit, Universiti Sains Malaysia, Minden
Campus, Penang. The cultures of S. oryzae were mass reared on local polished rice
(Beras Super Tempatan 15%, Zaa Edar Sdn. Bhd.), while T. castaneum was reared
on wheat flour (Prestasi Flour Mill (M) Sdn. Bhd.), both under laboratory conditions
at 30.0 ± 0.5ºC, 68 ± 2% relative humidity (RH), and 12 h photoperiod in round
plastic containers (10 cm in height x 9 cm in diameter).
3.2.2 Medium preparation
The choice of mediums was primarily determined by the availability of these
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rice grains, flour and starch in Malaysia’s commercial outlets. Eight different types
of rice grains used for rearing S. oryzae are shown in the table below (Table 3.1),
while six flour types and two types of starch tested against T. castaneum are shown
in Table 3.2.
Approximately 20 gm of each rice types (without dust), flour and starch were
placed into plastic containers measuring 4.5 cm in diameter and 9 cm in height,
respectively. The lids of each container were perforated to allow air movement which
helps prevent moisture buildup and inhibit fungal growth.
3.2.3 Assay
3.2.3.1 Sitophilus oryzae
Ten pairs of adult weevils (1 to 2-wk old), previously sexed according to
Halstead (1963) were placed into a container containing the respective rice types.
The experimental setup was replicated five times for each rice type. The weevils
were introduced and allowed to feed and oviposit for 7 d before they were removed.
They were then left in a cabinet held at 30.0 ± 0.5ºC, 68 ± 2% relative humidity
(RH), and 12 h photoperiod. Observations began as soon as the adults of the new
generation emerged from any eggs that might have been laid in the rice grains. All
newly emerged adults were counted and removed on a daily basis until no more
progeny emerged. At the end of the experimental period, the rice in each container
was weighed to determine the percentages of weight loss. The weight loss of rice
grains refers to emptied grains or any other remaining rice grains that are still intact.
Thus, prior to being weighed, the rice was sifted through a 4 mm wire-mesh to
remove any debris such as rice dust and frass.
3.2.3.2 Tribolium castaneum
Ten adult beetles (5 males and 5 females) of 7-d-old were introduced into the
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